Maraakate
Veteran Member
⚠⚠NOTE TO THOSE WHO USE THIS AS A GUIDE. WHEN I REFER TO BOLT SIZES I AM REFERRING TO THE SIZE OF THE HEAD⚠⚠
I'm not 100% ready for this yet, but figured I will start some documenting here.
I have 34,700 miles on my 79 CM400A. I originally had about 12,000 on it when I first got it back in 2011/2012. Maintenance has been done every year by me. Everyone has a different definition of this; in my case it meant setting valve clearances, cam chain tension and oil/filter change. I've replaced the drive chain once. Sprockets were still pretty good, funds were tight at the time but I was able to squeeze 10,000 miles out of this with regular, consistent oiling. I was using 90W gear oil for many years, but have finally switched to Maxima Chain Wax as the gear oil tends to make a mess. Compression still pretty decent at 155psi both sides. But let's do better and get it back to book spec of 185psi.
The plan here is to use all OEM parts. I got a spare 78 CB400T engine that was partially seized. The cylinder (not the head) is the same part number for 78 CB400A and 79 CM400A. I will be sending this out to get it bored 0.50 oversize. I also have another cylinder and a cylinder head coming from a 78 CB400A in case things are out of spec.
I'm also getting OEM intake and exhaust valves. If it is possible I will see if Kibblewhite could duplicate it based on a NOS valve, but I have not heard back yet and it may cost so much that it may be impractical for me to do so.
I'm slowly accumulating parts. All these kind of builds end up turning into a "while I'm in there..." type of project. So yes, the current plan is:
I have secured some parts already, and will be providing pictures as parts slowly accumulate. There won't be much progress here until riding season is over. Probably around December/January for me.
Total cost of parts, not including shipping is currently estimated at ~$915. So probably about $1000-$1100 over all. Does not include the balancer weights, but add another $20-$50 here and there, kinda/sorta/maybe. Machine work will be somewhere around $500... Add another $150-$200 for shipping. So, let's just throw an easy number out there say $2000 all together. Technically more than the bike is worth in some areas. It's not an investment for me. I'd like to keep it running and running correctly for years to come.
Current parts list and status can always be found here: https://docs.google.com/spreadsheets/d/1w3Sy89URxFIHhlzX6_lwiwnj-EWaOLyDFlIBPIHAx3U/edit?usp=sharing. Cosmetic pieces won't be ordered for this build (and are not calculated into the total). Not important right now. Anything grey means likely will not be ordering, but added to the list just in case.
Pictures of parts already acquired:
Head gasket
0.50" oversize rings.
Used cylinder.
There are three known problems with the bike that need addressed, thus the rebuild:
As far as I know, I don't really know of anyone else who has put this many miles on a Hondamatic, or have really rebuilt one and talked about it on here (besides Bill H @oldtimer). Should be interesting, fun, and a learning experience for me. I've never dived into bottom ends on larger stuff before. Only mopeds.
CURRENT STATUS AS OF 12-22-2023
Done! Thanks for everyone here for support and reading. Hope this helps someone in the future!
I'm not 100% ready for this yet, but figured I will start some documenting here.
I have 34,700 miles on my 79 CM400A. I originally had about 12,000 on it when I first got it back in 2011/2012. Maintenance has been done every year by me. Everyone has a different definition of this; in my case it meant setting valve clearances, cam chain tension and oil/filter change. I've replaced the drive chain once. Sprockets were still pretty good, funds were tight at the time but I was able to squeeze 10,000 miles out of this with regular, consistent oiling. I was using 90W gear oil for many years, but have finally switched to Maxima Chain Wax as the gear oil tends to make a mess. Compression still pretty decent at 155psi both sides. But let's do better and get it back to book spec of 185psi.
The plan here is to use all OEM parts. I got a spare 78 CB400T engine that was partially seized. The cylinder (not the head) is the same part number for 78 CB400A and 79 CM400A. I will be sending this out to get it bored 0.50 oversize. I also have another cylinder and a cylinder head coming from a 78 CB400A in case things are out of spec.
I'm also getting OEM intake and exhaust valves. If it is possible I will see if Kibblewhite could duplicate it based on a NOS valve, but I have not heard back yet and it may cost so much that it may be impractical for me to do so.
I'm slowly accumulating parts. All these kind of builds end up turning into a "while I'm in there..." type of project. So yes, the current plan is:
- Bore oversize to 0.50". OEM pistons and rings.
- New OEM intake and exhaust valves.
- New balancer chain.
- Changing the balancer weights to the later style that is a single, sealed unit from a 450.
- New cam chain.
- New cam chain tensioner.
- New cam chain sprocket.
- Refreshing the starter clutch with rollers, springs and caps. I will be inspecting if it or it's gears are junk and need replacement.
- All new o-rings and seals. All of them will be OEM.
I have secured some parts already, and will be providing pictures as parts slowly accumulate. There won't be much progress here until riding season is over. Probably around December/January for me.
Total cost of parts, not including shipping is currently estimated at ~$915. So probably about $1000-$1100 over all. Does not include the balancer weights, but add another $20-$50 here and there, kinda/sorta/maybe. Machine work will be somewhere around $500... Add another $150-$200 for shipping. So, let's just throw an easy number out there say $2000 all together. Technically more than the bike is worth in some areas. It's not an investment for me. I'd like to keep it running and running correctly for years to come.
Current parts list and status can always be found here: https://docs.google.com/spreadsheets/d/1w3Sy89URxFIHhlzX6_lwiwnj-EWaOLyDFlIBPIHAx3U/edit?usp=sharing. Cosmetic pieces won't be ordered for this build (and are not calculated into the total). Not important right now. Anything grey means likely will not be ordering, but added to the list just in case.
Pictures of parts already acquired:
Head gasket
0.50" oversize rings.
Used cylinder.
There are three known problems with the bike that need addressed, thus the rebuild:
- Balancer chain was never adjusted in 35K miles(whoops!). I was young, naieve and just never did it. I finally got around to doing it and it still amazingly has life left, but should be replaced.
- Many years ago, my dad and I put an Athena gasket kit on it as the cylinder started to weep between the cylinder and head. This cured the problem briefly, but returned a week later. Part of the reason is inferior gaskets used, but also because we both missed replacing the o-rings and seals in this area. Bike has been running fine with this minor leak for years. I always keep the oil topped off.
- Starter clutch is getting weak. It will freewheel if held longer than 2 seconds. Bike always starts pretty easy, so not a big deal... but might as well do it now. Over the years I've almost exclusively used the starter from dead cold and then have used the kickstarter throughout the day.
As far as I know, I don't really know of anyone else who has put this many miles on a Hondamatic, or have really rebuilt one and talked about it on here (besides Bill H @oldtimer). Should be interesting, fun, and a learning experience for me. I've never dived into bottom ends on larger stuff before. Only mopeds.
CURRENT STATUS AS OF 12-22-2023
Done! Thanks for everyone here for support and reading. Hope this helps someone in the future!
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